Applicators for applying a coating fluid for modifying surface properties of an article, such as a parting agent, an oil or a coating compound, to the surface of the article are composed of a coating member which is brought into direct contact with an article to be coated and a coating fluid holding member which holds a coating fluid and supplies the coating fluid to the coating member.
Large-sized coating equipment usually has a separate container, such as a tank, as a coating fluid holding member. For coating equipment with small consumption of a coating fluid, there is a coating fluid holding member which is used in the form integrated with a coating member.
Known coating fluid holding members of the latter type include a hollow pipe made of, e.g., metal having a number of small through-holes, with a coating fluid held in its hollow portion so as to be released little by little through the through-hole to a coating member provided in intimate contact with the outer surface of the pipe (see JP-U-59-73762 and JP-A-60-136782) and a synthetic resin foamed body having open cells, in which a coating fluid is infiltrated and oozed therefrom through capillary action (JP-B-61-6381). The terms "JP-U", "JP-A" and "JP-B" as used herein means an unexamined published Japanese utility model application, an unexamined published Japanese patent application, and an examined published Japanese patent publication, respectively.
A coating applicator should be such that a coating fluid can be applied at a constant rate without excess nor shortage. From this point of view, the stability of coating fluid supply is important for the above-mentioned type of coating fluid holding members which are not equipped with a constant delivery means, such as a pump. It is desirable for the coating fluid holding member to keep furnishing a fixed amount of a coating fluid in a stable manner from the start of use until the coating fluid held thereby is almost exhausted. It is also desirable for the coating fluid holding member to have as high a capacity as possible so that it may be used for as long a period of time as possible.
However, conventional coating fluid holding members having a high fluid holding capacity tend to cause considerable variation in feed rate with decrease of the residual coating fluid, while those having feed stability tend to have a small capacity and must be exchanged more frequently.